3D printed, mechanically tunable, composite sodium alginate, gelatin and Gum Arabic (SA-GEL-GA) scaffolds

Abstract

Biomimicking the mechanical properties of native tissues is one of the key requirements of engineering tissue scaffolds, rendering a need for materials and manufacturing processes with a high level of control over the mechanical properties of such scaffolds. To address this need, we present a 3D printable, composite hydrogel consisting of sodium alginate (SA), gelatin (GEL) and gum Arabic (GA), referred to herein as SA-GEL-GA hydrogel, mechanical properties of which can be controlled through tuning its cross-linking process. Here, the aqueous solution of the three constituents is used as the bioink to 3D print porous scaffolds in a temperature-controlled extrusion-based printing process. 3D-printed scaffolds are then crosslinked through a multi-step approach, realizing the gelation of GEL, ionic crosslinking of SA and GA, and covalent cross-linking of all three components. Here, we show that the inherent mechanical properties of SA-GEL-GA hydrogels can be controlled through the duration of the covalent crosslinking step. SA-GEL-GA bioinks exhibit highly temperature-dependent rheology with elastic solid-like behavior below room temperature and a viscoplastic, shear thinning nature above 28 ​°C. Using a cooled build-plate and heated printhead, high resolution scaffolds were printed with filament diameter of 250 ​μm and extruded from a 100 ​μm diameter nozzle. The compressive elastic modulus of these scaffolds can be tuned to the 50–250 ​kPa range through the combined effect of the scaffold pores size and covalent crosslinking step duration. 3D printed and crosslinked scaffolds carry over 500% of their dry weight in water and can be dried and reswollen to over 400% of their dry weight. Finally, our degradation analysis showed that increased covalent cross-linking duration led to reduced long-term structural stability due to mechanical failure of the scaffolds. These results indicate that SA-GEL-GA hydrogels offer exciting opportunities for manufacturing customizable artificial tissue scaffolds with biomimicking mechanical properties, particularly for soft tissues.